Mineral lubricating oil containing a combination of metal salts



mama Feb. 27, 1951 MINERAL LUBRICA'I'ING OIL CONTAINING A COMBINATION OF METAL SALTS William '1. Stewart and James 0. Clayton, Berke- Research ley, C

alif., assignors to California Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Application November 8, 1948, Serial No. 59,028

8 Claims. (Cl. 253-334) This invention relates to the art of improving organic substances by incorporating therein a small amount of an added agent which stabilizes the organic substance against oxidation, or reduces corrosiveness of said substance to particular kinds of metallic surface, or acts to disperse sludge in said subtance and prevent deposition of sludge on hot surfaces, or acts to prevent formation of sludge, or which functions to accomplish several of these objects.

More particularly, this invention relates to improving hydrocarbon oils of lubricating viscosity, such as mineral oil, motor, gear and turbine lubricants, transformer oils, mineral oil-soap greases, and the like, by adding thereto a small amount of an agent which stabilizes the oil against oxidation, or inhibits corrosion of cadmium-silver and lead-copper types of alloy bearings, or functions to prevent deposition of sludge and carbon on pistons and in piston ring slots of internal combustion engines, or functions to accomplish several of these results.

In the search for improved mineral lubricating oils, several desiderata are present, varying in importance from one type of service to another. Enhanced fllm strength (i. e., the ability of a lubricant to maintain a fllm of lubricant between relatively moving surfaces at extremely high pressures), resistance to discoloration on exposure to the normal atmosphere, as in storage of a lubricant, resistance to oxidation on exposure to air or other oxidizing gases at high temperatures as in transformers and in the lubrication oi. cylinders of internal combustion engines and the working parts of steam and gas turbines, and resistance to fouling of cylinders of internal combustion engines, are among the desired properties of lubricants and other mineral oil compositions.

It is an object of the present invention to provide a new class of materials for addition to oxidizable organic substances to satisfy one or more of the desiderata mentioned above.

It is a further object of the invention to provide compositions of matter comprising in major part an oxidizable organic liquid and containing a small amount of added organic substance which as such greatly enhances resistance of the composition to oxidation.

It is a further object of the invention to provide hydrocarbon lubricating oils and the like having high resistance to oxidation.

It is a further object of the invention to provide hydrocarbon lubricating oils of enhanced resistance to oxidation and to formation and de 2 position of sludge, and of reduced tendency to corrode cadmium-silver, copper-lead and other similar bearing alloys.

It is a particular object of the invention to provide mineral lubricating oils which are of enhanced utility as lubricants at high temperatures and in the presence of oxidizing gases, by reason of enhanced resistance to oxidation and reduced tendency to form or to deposit sludge on hot metal surfaces.

It is a further particular object of the invention to provide mineral oil lubricants for use in lubricating the pistons of internal combustion engines, especially of those engines, such as Diesel and aircraft engines, which operate under high It is also an object of the present invention to provide new, oil-soluble mineral oil improvement agents and a ready means of preparing the same.

It is also an object of the present invention to provide new combinations of mineral lubricating oil improvement agents, by means of which still more marked improvements and a greater variety of improvements are obtained.

Still further objects will be apparent from the ensuing description and the appended claims.

We have discovered that a certain class of selenium compounds, embracing many compounds in themselves new, when present in small amount in an oxidizable organic substance, impart marked improvements to the organic substance.

These selenium compounds are the salts of aliphatic selenomercaptans. Tellurium may be substituted for selenium, although the selenium compounds are preferred. These compounds may be represented by the formula wherein (reading from left to right), R1, R2 and R3 are hydrogen or organic radicals (any two of which may be Joined to form a single, bivalent radical), C is an aliphatic carbon atom (i. e., a carbon atom other than a carbon atom forming asearse part of a benzenoid ring), X is selenium or tellurium, and M is a salt forming radical.

The simplest member of this class is the metal salt of methyl selenomercaptan, CHaSeM. iii-- though it is operative as an improvement agent when added to lubricating oil and the like, it is somewhat volatile and not as well suited for use under high temperature conditions as are higher molecular weight, less volatile salts. The salts, however, have wider utility than the corresponding free selenomercaptan. Other similar low molecular weight selenomercaptides and telluromercaptides are likewise less desirable than the higher molecular weight (hence less volatile, less odorous and more oil-soluble) compounds.

The preferred compounds of the invention are those containing to 30 carbon atoms, most advantageously to 30 carbon atoms in the molecule. As stated. the selenium compounds are preferred to the tellurium compounds.

Examples of selenium and tellurium compounds of the invention are the sodium, calcium, barium and zinc salts of n-butyl, n-amyl, Z-ethylhexyl, decyl, lauryl, cetyl, octadecyl, and paraflin selenomercaptans and 2-ethylhexyl, lauryl and octadecyl telluromercaptans. Other radicals (e. g.; other alkyl radicals such as ethyl, nand isopropyl, isobutyl, isoamyl, hexyl, undecyl and tetrade'cyl, aralkyl radicals such as benzyl and cetylbenzyl and cycloaliphatic radicals such as cyclohexyl and methyl cyclohexyl), may be used in place of the above-mentioned radicals, and the organic radical attached to selenium may contain an unsaturated group or may be substituted by a non-hydrocarbon substituent such as chlorine, hydroxyl, alkoxyl, amino, etc. Examples of other metals and cationic salt-forming groups which may be used in place of sodium, calcium, barium and zinc are potassium, lithium, the ammonium radical, strontium, aluminum, cadmium, cobalt, nickel, lead and thallium.

By paraflin as used herein to designate an organic radical is meant a radical derived from paraffin wax; e. g., parafiin selenomercaptide is a selenomercaptide (actually, a mixture of selenomercaptides), such as can be prepared by using chlorinated parafiin wax as the organic chloride, R-Cl, in equation (2) below.

By aliphatic as used herein without qualification to designate an organic radical attached to selenium or te11urium,is meant an organic radical whose attachment to selenium or tellurium is through a non-benzenoid carbon atom; e. g., octadecyl, benzyl and cyclohexyl selenomercaptans are all aliphatic" selenomercaptans as aliphatic is herein defined and may be employed as metal salts in accordance with the present invention.

The selenomercaptans used for subsequent conversion to salts can be prepared by the following series of reactions:

Sodium diselenide is prepared by reaction (1) and is reacted with an aliphatic chloride (RC1) in accordance with reaction (2) to yield an aliphatic diselenide (R-SeSeR). The aliphatic diselenide is reduced in accordance with reaction (3 to yield an aliphatic selenomercaptan.

In reactions (1), (2) and (3), potassium or other metal may be substituted for sodium, tellurium may be used instead of selenium and bromine or other replaceable element or radical may a be substituted for chlorine. aliphatic group. If a mixed diselenide is available, e, g., ethyl cetyldiselenide (Cal-Is SeSe CmHss) it may be substituted for the symmetrical diselenide of reaction (3), yielding a mixture of selenomercaptans (e. g., ethyl and cetyl selenomercaptans).

The salts of selenoand telluromercaptans can be prepared in various ways. Thus a selenoor telluromercaptan may be dissolved in an aqueous, or aqueous-alcoholic solution of sodium or potassium hydroxide and sodium or potassium selenoor telluro-mercaptide can be recovered from the solution by evaporation of the solvent. or an aqueous solution of a water-soluble polyvalent metal salt, a. g., zinc sulfateor calcium chloride, may be added to an aqueous solution of alkali metal selenoor telluromercaptide, thereby precipitating a water-insoluble polyvalent metal selenoor telluromercaptide. Still other methods of preparing these salts are illustrated in the specific examples below; The salts prepared by crystallization from a suitable solvent such as chloroform or ethyl alcohol.

The selenium and tellurium compounds of the invention may be used in amounts as low as 0.01% or less or as high as 5% or more, but preferably they are used in amounts of 0.1 to 2%, percentages being by weight based on finished composition. Concentrates or stock solutions containing 5 to 50% or more of the selenium compound of the invention dispersed in an organic liquid (e. g., mineral lubricating oil) may be prepared for later blending with the substance to be stabilized to prod-Ace a finished product.

Illustrative of organic substances to which the selenium compounds of the invention may be added as stabilizers are petroleum products such as saturated gasoline, kerosene, lubricating oils and mineral oil-soap greases; saturated fats, fatty oils, rubber, aldehydes, ethers, terpenes, mercaptans, phenols and synthetic plastic or resinous materials such as urea-formaldehyde, polyvinyl and phenol-formaldehyde resins.

Since selenomercaptides do not react with unsaturated compounds as contrasted to selenomercaptans which apparently react with certain olefins such as in cracked gasoline, the present agents may also be used to inhibit oxidation of oxidizable unsaturated organic substances (analogous to the above-listed substances), such as cracked gasoline, etc., and unsaturated fats, fatty oils, and the like. Thus, the selenomercaptides as such are effective oxidation inhibitors and do not tend to react with the oxidizable organic substance which is desired to inhibit against oxidation. These and other organic materials undergo oxidation and deterioration (e. g., discoloration, sludge formation, thickening, etc.) under conditions ranging from mere exposure to air at normal atmospheric temperatures to intimate admixture with air or other oxidizing gases at temperatures of 300-400 F. The inherent stability of the organic material toward oxidation will, of course, vary with the material. The selenium compounds of the invention will stabilize such materials under mild to extreme conditions of oxidation.

The following specific examples will serve further to illustrate the practice and advantages of the invention.

Example 1.-Preparation of high molecular The group R is an amass weight selenomercazrtaria-Methods described in the literature for preparing selenomercaptans are the. reaction of sodium or magnesium hydroselenide with an alkyl halide or alkyl metal sulfate, and the reaction of aluminum selenide with alcohols at elevated temperatures. See, for example, J. Newton Friend's Textbook of Inorganic Chemistry," vol. XI, part IV, page 1 (1937). These methods are disadvantageous because large amounts of dialkyl selenides and dialkyl diselenides are formed by side reactions. This necessitates the recovery of the selenomercaptan by distillation When applied to the preparation of high molecular weight selenomercaptans, i. e., those containing about 10 carbon atoms or more,

' these methods of the prior art are especially dis-' advantageous because of the tendency of the high molecular weight selenomercaptans to decompose on distillation.

We have discovered a much superior method of preparing high molecular weight selenomercaptans which will now be described with reference to octadecyl selenomercaptan.

Dioctadecyl diselenide was prepared as follows: A mixture of 2 gram moles of sodium diselenide, 2 gram moles of octadecyl chloride and one liter of 95% ethyl alcohol were refluxed and stirred for nine hours. The reaction mixture was diluted with one liter of water and extracted with petroleum ether. The petroleum ether extract was dried over anhydrous sodium sulfate, filtered and concentrated on a steam bath. Two volumes of a 50% mixture of petroleum ether and acetone were added and the solution was cooled to promote crystallization of the dioctadecyl diselenide. A yield of 602 grams of dioctadecyl diselenide was obtained in the form of lemon yellow crystals melting at 52 C. to 55 C. Analysis.--Found: Percent Se=22.3. Theoretical: Percent Se=2'3.8.

A mixture of 30.4 grams of dioctadecyl diselenide and 34 mls. of 50% (by weight) sulfuric acid was heated to reflux temperature and 8.7

grams of zinc dust were added gradually with vigorous stirring. After addition of the zinc dust had been completed, 5 mls. of concentrated sulfuric acid were added and refluxing and stirring were continued until the zinc had completely reacted. On cooling the mixture to room temperature, octadecyl selenomercaptan separated as a white crystalline layer. This product was a white, waxy, crystalline solid melting at 36 to 40 C.

The octadecyl selenomercaptan so prepared can be reacted with alcoholic solutions of metal hydroxides or metal acetates to yield the desired metal selenomercaptide, or it can be dissolved in aqueous or aqueous-alcoholic sodium or potassium hydroxide and treated as described above.

Example 2.Preparation of zinc octadecyl selenomercaptide-The product of Example 1 (product of reducing 30.4 grams of dioctadecyl di selenide) was extracted with petroleum ether and the extract was washed with water, dried over sodium sulfate, filtered and mixed with 200 ml. of 95% ethyl alcohol. Petroleum ether was removed by distillation and 250 ml. of 95% ethyl alcohol were added to the residue. This mixture was heated to 150 F. and a solution of 18.3 grams of zinc acetate dissolved in 150 ml. of hot water was added slowly with stirring. A white precipitate formed, which was collected on a filter, washed with water, then with alcohol and then with petroleum ether and dried in vacuo over calcium chloride. A yield of 22 grams of zinc octadecyl selenomercaptide was obtained, being 65% on the crude dioctadecyl diselenide. This 6 product was found to contain 20.7% Se (theoretical, 21.6%) and 8.91% Zn (theoretical, 8.95%). In subsequent preparations, the yield was raised We 84%. The product was a white solid soluble in chloroform and benzene, slightly soluble in alcohol.

Example 3.-Preparation of cadmium octadecyl selenomercaptide-A solution of 70.4 grams of cadmium acetate dihydrate in 300 ml. of hot 50% ethyl alcohol was added slowly with stirring to a hot mixture of 160 grams of octa. decyl selenomercaptan and 300 ml. of 100% ethyl alcohol. The precipitated cadmium octadecyl selenomercaptide was collected on a filter, washed with water, alcohol and acetone and dried in. vacuo over calcium chloride.

The product weighed 188 grams, representing a yield of 60% based on cadmium content. Analysis.Found: Cd=8.7%, 8.8%; Se=16.6%, 16.8%. Theoretical: Cd=14.5%, Se=20.3%. After extraction with boiling petroleum ether, the product weighed 145 grams and assayed 11.5% Cd and 19.8% Se. The product was a white solid, soluble in chloroform and benzene and slightly soluble in alcohol. The product was about pure.

Example 4.Preparation of lead octadecyl selenomercaptide.-A hot solution of 91.2 grams of basic lead acetate (Pb2(OH)A03) in 350 ml. of 50% ethyl alcohol containing 9 grams of glacial acetic acid was added slowly with stirring to a heated mixture of 200 grams of octadecyl selenomercaptan and 350 ml. of 100% ethyl alcohol. The precipitate was filtered off, washed with hot water, alcohol and petroleum ether. After drying in vacuo over calcium chloride the product weighed 205 grams, representing a yield of 78% based on lead content. Analysis.-Found:

Pb=23.5%; S8=17.7%

Theoretical: Pb=23.8%; Se=l8.1%. The product was a salmon-colored solid, soluble in chloroform and benzene, and slightly soluble in alcohol.

Example 5.Preparation of barium octadecyl selenomercaptide.-A slurry of 43 grams of barium oxide in 200 ml. of ethyl alcohol and 5 ml. of water was added with stirring to a refluxing mixture of 180 grams of octadecyl selenomercaptan and 200 ml. of 95% ethyl alcohol. Refluxing was continued for twenty-five minutes and the reaction mixture was allowed to cool. The precipitate was collected on a filter, washed with alcohol and petroleum ether and dried in vacuo over calcium chloride. The product weighed 184 grams representing a yield of 77% based on barium content. Analysis.-Found: Ba=l5.8%; Se=17.6%. Theoretical: Ba=17.l%; Se=19.7%. The product was slightly soluble in chloroform and benzene.

Example 6.Preparation of nickel octadecyl selenomercaptide-A hot solution of 69.2 grams of nickel bromide in 250 ml. of 50% ethyl alcohol was added with stirring to a heated mixture of 214 grams of octadecyl selenomercaptan and 350 m1. of ethyl alcohol. Stirring was continued while a solution of 25.8 grams of sodium hydroxide in ml. of hot water was added slowly. The precipitate was collected on a filter, washed with acetone and dried in vacuo over calcium chloride. The product weighed 242 grams. Analysis.--Found: Ni=6.8%, 6.8%; Se=l6.1%, 16.2%. Theoretical: Ni=8.l%; Se=22.0%. Fractionation of the product showed it to be a mixture of nickel octadecyl selenomercaptide (38%), octadecyl selenomercaptan and diocta- 7 decyl diselenide (37%)v and inorganic nickel compounds. The crude product was a granular, black solid, soluble in chloroform and benzene.

In each of the preparations described in Examples 1 to 6, above, the reaction mixture and product were blanketed by an atmosphere of nitrogen to prevent oxidation, until such timeas the final product was prepared.

Example 7.O:z:idator tests.-Selenium cornpounds of the invention, also, for comparison, certain selenium compounds not of the invention, were dissolved in small amount in medicinal grade of white oil and submitted to an oxidation test in an apparatus of the type described by Dornte in Industrial and Engineering Chemistry, vol. 28, page 26 (1936), oxygen being bubbled through the oil at atmospheric pressure. The temperature of the oil was 340 F. Results are given in Table I below, the Induction period" being the time in hours required for 100 gms. of oil to absorb 1200 cc. of oxygen measured at S. T. P.

It will be seen from the above table that all of the additives of the invention greatly improved the base oil. The free selenomercaptan was superior to dioctadecyl and dilauryl selenides. The metal selenomercaptides. were not as effective oxidation inhibitors as the selenomercaptan, but several were as effective as dialauryl selenide and all of them greatly improved the base oil.

As oxidation inhibitors the free selenomercaptans are preferred to their salts, but their salts, especially the polyvalent metal salts, have in greater degree the property of functioning as detergents in motor lubricants; i. e., they promote cleanliness of pistons, piston rings and piston ring slots and retard piston ring sticking in internal combustion engines. This is shown in Example 8 and Tables II and III below.

Example 8.Strip corrosion and engine tests.- Various oils,v both uncompounded and compounded with small amounts of additives as indicated in Tables II and III below, were submitted to strip corrosion and engine tests as follows: In the corrosion tests, thin strips of copper-lead alloy of the type used in bearings of internal combustion engines are immersed in oil.

The oil is maintained at 300 F. and air is blown through the oil during the test. Corrosion loss is noted after each test. Further details of this test appear in Farringtonet al. U. S. Patent No. 2,349,817 at page 3, right-hand column, lines 1'7 to 37. The Lauson engine tests were carried out in the manner described in the same patent, page 3, left-hand column, lines 14 to 26, except that observations were made only at 30-hour intervals, crankcase (sump) temperature was 300 F., and the engine speeds were 1800 R. P. M. (Table II) and 1200 R. P. M. (Table III). The Wisconsin tests were carried out in a single cylinder aircooled Wisconsin engine 2% bore and 2% inch stroke, loaded by means of an electric induction motor. The engine was operated under extremely severe conditions, designed to develop fully the tendency of the crankcase lubricant to deteriorate with gum formation-and piston ring sticking. Operation was at 1300 R. P. M.; upper cylinder temperature was maintained at 600 11; crankcase oil temperature was maintained at 220 F. At periods of 30 hours the operations were interrupted and the condition of the piston and piston rings determined.

The results of these tests are set forth in Tables II and III below. In the tables, the concentration of each additive, if it is a salt, is given as millimols of metal per kilogram of oil; e. g., "14 mM/kg. Zn octadecyl selenomercaptide, which means 14 millimols of zinc, in the form of zinc selenomercaptide, per 1000 grams of oil. This particular salt was a relatively pure compound, (C1aH3'1Se)2ZI1, and has a molecular weight of 729. Therefore, 14 mM/kg. of this salt amounts to 1% by weight salt based on the oil. In most other cases the mM/kg..of metal can be similarly converted to per cent by weight of salt but in a few cases, e. g., calcium sulfenate, the molecular weight of the salt being unknown, it is impossible to convert mM/kg. of metal to per cent of salt. 7

Further with regard to Table II: The calcium sulfonate was a synthetic product made by chlorinating white oil, then condensing it with benzene, sulfonating the condensation product and converting the sulfonic acid to its calcium salt. The calcium phenate was prepared by condensing a butene polymer (average molecular weight about 194) with phenol and forming the calcium salt of the condensation product, as described in Examples 1 and 3 of Gardiner et al. U. S. Patent No. 2,228,661. The sulfurized calcium phenate was prepared by heating the same calcium phenate with sulfur, as described in Etzler et al.- U. S. Patent No. 2,360,302. The zinc dicetylphenyl dithiophosphate was the product of reacting two moles of cetyl phenol, one mol of P285 and one mole of ZnO. The sulfurized diparaflin sulfide was the product of reacting chlorinated paramn (22% chlorine) with sodium polysulfide to yield a product containing 14% sulfur and 3% chlorine and heating this sulfurand chlorine-containing product with free sulfur in the proportions of 100 and 4.2, respectively, at 300 F. until all the sulfur dissolved. The said sulfurand chlorine-containing product can be prepared in the manner described in Example 1 of Farrington et al. U. S. Patent No. 2,346,156. All the salts of Table II were normal salts. Base oil A was a solvent refined SAE 30 parafllnic oil of California origin. Base oil B was a solvent refined SAE 30 Mid-Content oil. Oil C was a solvent refined SAE paraffinic oil of California origin.

In these tables, "PD No. designated piston discoloration number. By piston discoloration number is meant this: After 30 hours and again after hours, the engine is disassembled and the piston is inspected. To a piston skirt which is completely black is assigned a PD No. of 800; to one which is completely clean is assigned a PD No. of zero; to those intermediate completely black and completely clean are assigned PD Nos. in proportion to the carbonaceous deposits. Actually, further refinements were employed in ar-- riving at PD Nos. hereinbelow disclosed, but since the same method was used in every case it is unnecessary to describe these refinements.

Table II-strip corrosion and Lemon enema tests Strlp Omar-Wt. Lou, Eng no? A d d1 a" m D N- 24 Hrs. 48 Hrs. 72 Hrs. 30 Hrs. 00 Hrs.

A Nil.-. I l. l 48. 6 108. 7 400 A 14 mM/kg. Ca sulionate l1. 1 30. 6 62. 2 150 245 A 14 mM/kg. Zn octadecyl aelenomercaptide.. 25. 5 22.8 25.2 70 310 A 14 mM/kg. Cd octadec l selenomercaptide. +3. 8 +8. 7 +6. 6 130 165 A l4 mM/kg. Sulfurized a phenate. 210 m A 7 mM/kg. Zn octedecyl selenomemaptide+7 mM/kg.

suliurimd Ca phenete +6.1 +8.6 +11.3 110 215 A .7 mM/kg. Pb octadecyl selenomercaptide+7 mM/kg. A fi ged a p g e- +6.1 +4.6 +3.1 $8

In a t I V A 7 mM/kg. Zn octsdecyl selenomerceptide+7 mM/kg. Ca

phenom 8. 8 l8. 7 32. 0 7!) 26 A 7 mM/kg. Cd octadecyl selenomerceptide+ 7mM/kg. Ca

phenafn 18. 4 18. 9 2). 0 40 75 A 7 mM/kg. Be. octadecyl selenomercaptide+7 mM/kg. 0a

phen 91. 0 02. 9 we 5 H) 85 A 7 mM/kg. Ca sulionate+7 mM/kg. Zn octadecyl solenomercsp +2. 6 +6. 8 +10. 7 86 Table III-Strip corrosion and engine tests Strip Corrosion-Wt. Loss, Engineests-PD Base m 0! on Additives E23 24 Hrs. 48 Hrs. 72 His. Hrs. Hrs.

B Reference Cnmpmmdlnv 1. 1 1. 4 2. 9 200 Lauson. B 4.5 mM/kg. sulfurized Ca phenate+4.5 mM/kg. Ca +6.8 +8.1 +8.7 5 10 Do.

indlfonate+6 mM/kg. Zn octadecyl selenomercepe. B 9 mM/kg. Os aphenate+6 mM/kg. Zn octadecyl 60 60 Do.

selenomercapt de. 0 Nil 1.3 4.4 21.0 465 Wisconsin. 0 0.8% Octadecyl selenomercaptan+16 mM/kg. Ba 1.3 7.0 16.6 75 106 Do.

m-oetoxy phenate. C 16 mM/kg. Zn octadecyl selenomercaptide 0.1 +1. 0 +12. 6 216 320 Do. 0 8 mM/kg. Zn octadecy selenomercaptide+8 mM/kg. +9. 5 +7. 0 +6. 0 Do.

Ba m-cetoxy phenate. C 8 mM/kg. Ca phenom-+8 mM/kg. Zn octadecyl 8. 1 28.0 41.4 1.15 145 Do.

selenomercaptide. C 14 mM/kg. Ca phenate+14 mM/kg. Zn octadeeyl 17.8 18. 1 31.4 106 135 Do.

' selenomercaptide. C 24 mM/kg. Ca Iphonate+l4 mM/kg. Zn octadecyl 5. 8 4.2 7.2 130 D0.

selenomercapt de. 0 7 mMkg. Ba m-eetoxy ghenate+7 mM/kg. Pb 8.8 9. 1 9.4 136 Do.

octa ecyl selenomercapti e.

In Table IV below are given still further data,

The reference compounding" in base 011 B showing the performance of a low molecular 45 was a multipl compounding which has passed weight selenomercaptide (zinc 2-ethyl hexyl selenomercaptide, made from z-ethyl hexyl chloride) and of a high molecular weight selenomercaptide (zinc paraflln selenomercaptide, made from a chlorinated, low melting paraflin wax). Base oils 50 A and C are the same as base oils A and C above.

exacting test requirements of Army Ordnance 2-1043 Specification. The superiority of the compounding of the present invention is evident form Table 111.

One or more selenium compounds of the invention may be used as the only added material Table IV Strip Corrosion Wt. Lou, Engine goats-PD Bose 01' on Additives fig 24Hrs. 481111. 721111. 301111;. 00Hrs.

-A v 4.5 mM/kg. Ca sulfonate+4.5 mM/kg. sulfurized Ca +11. 5 +13.0 +125 0 0 Lauson.

phengte+6 mM/kg. Zn 2-ethyl hexyl selenomerea c. C 20 mM/kg. Ca phenate+l0 mM/kg. Zn 2-ethyl hexyl 7. 8 3. 8 2. 3 160 225 Wisconsin.

selenomercaptide. C 8 mM/kg. Ca phenate+8 mM/kg. Zn paraflin seleno- +9. 4 +21. 4 +21. 4 40 50 Do.

mereaptide.

The data in Tables II, III and IV illustrate, among other things, the following: Most of the selenium compounds of the invention functioned to inhibit corrosion of copper-lead bearings. All of them functioned to promote piston cleanliness, as shown by the PD numbers. Especially good results were obtained with combinations of addition agints, such as the phenate-selenomercaptide, sulfurized phenate-selenomercaptide and sulfonate-selenomercaptide combinations,

present in an oxidizable organic substance or they may be used in conjunction with other additives. For example, the selenium compounds of the invention may be used advantageously in mineral lubricating oils in conjunction with metal salts of organic acids and/or metal salts of organo-substituted inorganic acids. These salts are used to improve various properties of lubricating oils, such as detergency, stability against oxidation, film strength, etc. Examples of such metal 11 salts are calcium, barium, zinc and aluminum salts of cetylphenol; calcium, barium, zinc and aluminum salts of diamyl diphenol monosultide; calcium, barium, zinc and aluminum salts of monoand dicetyl esters of phosphoric acid; calcium, barium, zinc and aluminum salts of monoand dicetylphenyl esters of dlthiophosphoric acids; calcium, barium, zinc and aluminum salts of naphthenic acids; calcium, barium, zinc and aluminum salts of oil-soluble petroleum (mahogany) sulionic acids; calcium, barium, zinc and aluminum salts oi dibutyl dithiocarbamic acid; calcium, barium, zinc and aluminum salts of the reduced petroleum nitrogen base dithiocarbamates of Miller and Rutherford U. S. Patent No. 2,363,012. Other metals (e. g., sodium, lithium, magnesium and cobalt) and other acid radicals (e. g., aryl carboxylic acid, fatty acid, aliphatic polycarboxylic and thiophenol radicals) may be used instead or the aforementioned calcium, barium, zinc and aluminum metals and the aforementioned phenate, phenate sulfide, phosphate, thiophosphate, naphthenate, sulfohate and dithiocarbamate radicals, respectively. Thus, from 0.1 to 2% of selenium compound and from 0.1 to 2% of metal salt may be added to mineral lubricating oil, or greater amounts may be used to form a concentrate or stock solution.

The selenium and tellurium compounds of the present invention are also useful to improve the film strength of lubricants. as shown by the following data:

Table V Failure (Weeks Testln%Machlne, NOR. .M.)at

Pounds Solvent refined SAE 30 oil 100 Solvent refined SAE 30 oi1+0.5l% octadecyl selenomercaptan 180 Solvent refined SAE 30 oil+0.5d% Zn octadecyl selenomercaptide 340 proportion of mineral oil and dissolved therein about 0.1 to about 2% by weight based on the finished oil of an oil soluble polyvalent metal salt of a compound selected from the group consisting of phenates and aromatic sultonates, and about 0.1 to about 5% by weight of a polyvalent metal salt of an alkyl selenomercaptan containing 5 to 30 carbon atoms in the molecule.

2. A mineral lubricating oil comprising a major proportion of mineral lubricating oil, and dissolved therein about 0.1 to 2% by weight based on finished oil of an oil-soluble polyvalent metal sulfonate and about 0.1 to 2% by weight of a polyvalent metal salt of an alkyl selenomercaptan containing 5 to 30 carbon atoms in the molecule.

3. A mineral lubricating oil comprising a major proportion of mineral lubricating oil, and dissolved therein about 0.1 to 2% by weight based on finished oil of an oil-soluble polyvalent metal salt oi a phenol and about 0.1 to 2% by weight of a polyvalent metal salt of an alkyl selenomercaptan containing 5 to 30 carbon atoms in the molecule.

4. The oil of claim 3, wherein said metal salt of a phenol is an alkaline earth metalsalt of an alkylated phenol containing in the molecule two phenate nuclei linked by sulfur.

5. The composition of claim 1, wherein the metal salt of an alkyl selenomercaptan is zinc selenomercaptlde.

6. The composition of claim 5, wherein the mercaptide is zinc 2-ethylhexyl selenomercaptide.

7. The composition of claim 5, wherein the mercaptide is zinc octadecyl selenomercaptide.

8. The composition or claim 5, wherein the selenomercaptide is lead octadecyl selenomercaptide.

T. STEWART. JAMES 0. CLAYTON.

REFERENCES orrun The following references are of record in the file of this patent:

UNITED STATES m'mu'rs Number Namev Date 1,835,184 'Rosenstein Dec. 8, 1931 2,125,961 Shoemaker Aug. 9, 1938 2,263,445 Reif Nov. 18, 1941 2,274,302 Mulit Feb. 24, 1942 2,289,795 McNab July 14, 1942 2,362,292 McNab Nov. 7, 1944 2,398,415 Denison et a1 Apr. 16, 1946 

1. A MINERAL LUBRICATING OIL COMPRISING A MAJOR PROPORTION OF MINERAL OIL AND DISSOLVED THEREIN ABOUT 0.1 TO ABOUT 2% BY WEIGHT BASED ON THE FINISHED OIL OF AN OIL SOLUBLE POLYVALENT METAL SALT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF PHENATES AND AROMATIC SULFONATES, AND ABOUT 0.1 TO ABOUT 5% BY WEIGHT OF A POLVALENT METAL SALT OF AN ALKYL SELENOMERCAPTAN CONTAINING 5 TO 30 CARBON ATOMS IN THE MOLECULE. 